White blood cells (“WBC”), also referred to as leukocytes, aid the human body in fighting infectious diseases by defending against foreign materials, such as bacteria and viruses. White blood cells play an essential role in the natural defense system, which is provided by the immune system of the human body. The number or ratio of white blood cells in the body is often used as a diagnostic of disease. For example, a consistently high number of white blood cells in the body is a strong indicator or symptom of Leukemia, a blood cancer. White blood cells are useful in a variety of medical fields, including immunology, cancer research, and other fields.
In both human and animal blood, white blood cells are mixed with other components, such as red blood cells (“RBC”). Therefore, there is a need to isolate or separate the white blood cells from the other ingredients in the blood. Current methods for the isolation of white blood cells from bodily fluids continue to be cumbersome. In general, the blood sample is mixed with an anticoagulant (e.g., EDTA), centrifuged, the plasma is removed, and the buffy coat (which forms a thin layer on top of the RBCs) is transferred to another tube and used. Under these conditions, the buffy coat contains the white blood cells as well as low levels of contaminating red blood cells and platelets. Alternatively, various red blood cell lysing buffers are added to the blood sample and the sample is centrifuged. While the latter procedure leads to the rupture of most of the red blood cells present, the non-lysed RBCs no longer sediment faster than the white blood cells and are found above the white blood cells in the centrifuge tube.
Oftentimes, such red blood cell contaminated white blood cell preparations negatively affect the downstream usage of white blood cells. For example, >99% of the cellular blood fraction is composed of red blood cells. While mature RBCs lose their nuclei and various organelles during maturation and thus do not contribute any RNA to the total RNA pool, immature RBCs (known as reticulocytes) often contain residual nucleic acids. Since ˜1% of RBCs are reticulocytes, residual RNA (mostly globulin mRNA) from these cells contributes ˜70% of the RNA in the total blood RNA pool. Globin mRNA can compromise the detection of other specific mRNAs from leukocytes. Heme is also present at relatively high concentrations in RBCs. If heme is not adequately removed during RNA isolation of WBCs, it too can significantly impair downstream analyses such as microarray analysis and RT-PCR. Therefore, there is a strong need in the art for a process that rapidly isolates white blood cells from bodily fluids that are void of red blood cell contaminations.